There is an image forming apparatus that forms an image with decolorizable material, which is decolorized by heating. When paper having an image formed with the decolorizable material is subjected to an erasing process, during which heat is applied to the paper by an erasing apparatus, the image is erased. Thus, the paper can be repetitively used for printing. Conventionally, such an erasable image is formed with one type of decolorizable material. Thus, the erasable image can be formed only with the color of the decolorizable material.